The invention broadly relates to (i) pads of pressure sensitive adhesive tape strips, (ii) dispensers for tape strip pads, and (iii) methods of dispensing individual tape strips from tape strip pads.
Numerous types of pressure sensitive adhesive tapes capable of connecting or joining two surfaces (e.g., adhering a sheet of paper onto a table top) are well known. For example, #810 Scotch(trademark) Magic(trademark) brand transparent tape, manufactured by Minnesota Mining and Manufacturing Company, St. Paul, Minn. is readily available from numerous retail outlets. Such pressure sensitive adhesive tapes, including #810 Scotch(trademark) Magic(trademark) brand transparent tape, are generally available as a continuous roll of tape capable of being conveniently dispensed from any of a number of manually-operated roll-type tape dispensers, such as those disclosed in U.S. Pat. No. 4,928,864 and U.S. Design Pat. No. 116,599, having a cutting edge located on the dispenser for cutting the tape into strips of the desired length. While effective for quickly and efficiently dispensing most pressure sensitive adhesive tapes, it is difficult to create tape strips of uniform length due to the natural variations in the length of tape unwound from the roll of adhesive tape between cuttings. Hence, such dispensers are not suitable for those situations requiring the quick and efficient dispensing of uniform lengths of pressure sensitive adhesive tape.
It is also known to dispense pressure sensitive adhesive tape, such as Scotch(trademark) Magic(trademark) brand transparent tape, from a stacked pad of tape strips. Such pads of adhesive tape strips are disclosed, U.S. Pat. Nos. 4,650,706, and 4,895,746. Both ""706 and ""746 disclose stacked pads of adhesive tape strips wherein a first end portion of each individual strip is treated so as to provide a nonadhesive end tab (""706) or an area of reduced adhesion to an adjacent tape strip (""746) at a first end of the pad. The nonadhesive end tab or area of reduced adhesion facilitates initial separation of the first end of an uppermost tape strip from the first end of an immediately underlying tape strip, allowing the uppermost tape strip to be peeled off the pad. While generally effective for dispensing uniform lengths of pressure sensitive adhesive tape, such pads are somewhat cumbersome to use and are not well suited for use in those situations where only one hand is available for dispensing the tape, such as gift wrapping.
Post-it(copyright) brand notes and Post-it(copyright) brand flags, available from 3M of St. Paul, Minn., require a coating of releasable pressure sensitive adhesive only along one end of the substrate, and can therefore be conveniently dispensed from a container by alternating the adhesive end of the stacked sheets/flags between opposed first and second ends of the stack (e.g., forming a Z-stack of sheets). Such a stack of Post-it(copyright) brand flags and associated shuttling dispenser is disclosed in U.S. Pat. No. 4,770,320. Similarly, a pad of W-stacked sheets and associated dispensers are disclosed in U.S. Pat. Nos. 4,416,392, 4,562,938, 4,586,629, and 4,653,666. This alternating style of stacking the sheets/flags is effective because the sheets/flags are adhesively bonded together with a repositionable pressure sensitive adhesive on only one end of the sheet/flag. Such sheets are not suitable for joining or connecting surfaces together because of the relatively small percentages of such sheets coated with adhesive and the low adhesion strength of the pressure sensitive adhesive used with such sheets/flags.
A significant advance in the construction and dispensing of pads of adhesive tape strips is disclosed in U.S. Pat. No. 5,401,547. ""547 discloses a pad of superimposed adhesive tape strips wherein the adhesive layer of each tape strip is releasably adhered to an adjacent tape strip at a first adhesion level at a first end and a second adhesion level at a second end (i.e., differential release), and sequential tape strips are longitudinally reversed so as to align the first end of each tape strip with the second end of an immediately overlaying and an immediately underlying tape strip. A preferred manner of achieving such differential release disclosed by ""547 is to coat the entire surface area of a first major surface of each strip with a pressure sensitive adhesive and coat the second end portion of the second major surface of each tape strip with a low adhesion backsize (LAB). Such an alternately stacked pad of differential release tape strips can be conveniently dispensed from an associated dispenser with a single hand while maintaining a continuous coating of an aggressive pressure sensitive adhesive on the substrate.
While constituting a significant improvement, the pads disclosed by ""547 comply with a specific set of release levels in order to achieve the sliding action required between adjacent tape strips for proper dispensing while preventing fanning of the stacked strips (i.e., preventing the tape strips from accidentally and unintentionally sliding relative to one another before each strip is dispensed). Furthermore, as described in ""547, when the differential release requirement is achieved, that portion of the tape strip coated with the premium LAB does not consistently maintain any written indicia.
Accordingly, a substantial need exists for a pad of adhesive tape strips and/or a dispenser for such pads that will provide the convenience of one hand dispensing, provide wider manufacturing parameters, and provide a broader range of release/adhesive systems than the pads of adhesive tape strips disclosed by ""547.
Briefly, in one aspect of the present invention a dispensing technique is provided for consistently dispensing individual tape strips from a category of W-stacked pads of adhesive tape strips previously believed to be incapable of being dispensed without a high incidence of dispensing failures (i.e., multi-strip dispensing or tail off). Dispensers are also provided that dispense individual tape strips from W-stacked pads of adhesive tape strips using the novel technique and have significantly expanded the types of tape strips capable of being dispensed in the form of a W-stacked pad of tape strips.
For purposes of clarity and without intending to be unduly limited thereby, the tape strips in a group of any three sequentially stacked tape strips are referenced as an overlying tape strip, an intermediate tape strip, and an underlying tape strip with the adhesive layer of the overlying tape strip adhered to the intermediate tape strip, and the adhesive layer of the intermediate tape strip adhered to the underlying tape strip.
The novel technique for dispensing an overlying tape strip from a W-stacked pad of differential release tape strips involves (i) pulling the second longitudinal end of an overlying tape strip away from the pad so as to effect peeling of the overlying tape strip from the intermediate tape strip in a progressive fashion from the second longitudinal end of the overlying tape strip towards the first longitudinal end of the overlying tape strip, (ii) contacting the overlying tape strip so as to restrict the peel angle between the overlying tape strip and the intermediate tape strip to an angle of less than 45xc2x0 prior to complete separation of the overlying tape strip from the intermediate tape strip and prior to release of a second longitudinal end section of the intermediate tape strip from the underlying tape strip, and then (iii) continuing to pull the overlying tape strip away from the pad to sequentially effect release of the second longitudinal end section of the intermediate tape strip from the underlying tape strip, and complete separation of the overlying tape strip from the intermediate tape strip.
Novel dispensers capable of dispensing a W-stacked pad of adhesive tape strips using the novel dispensing technique described herein comprise (i) a housing defining a retention chamber for holding a W-stacked pad of adhesive tape strips, and having a top with a substantially centrally positioned opening for permitting passage of an adhesively bonded combination of a first longitudinal end portion of an overlaying adhesive tape strip and a second longitudinal end portion of an immediately adjacent intermediate tape strip from a W-stacked pad of adhesive tape strips retained within the retention chamber, and (ii) a means for engaging the overlaying adhesive tape strip as the overlaying adhesive tape strip is dispensed through the opening so as to invariably provide a low peel angle between the overlaying adhesive tape strip and the immediately adjacent intermediate adhesive tape strip at the point of release of the second end portion of the intermediate adhesive tape strip from an adjacent underlying adhesive tape strip. Generally, the engagement means is preferably positioned at both longitudinal ends of the dispenser so as to provide a peel angle of less than 45xc2x0 with a longitudinal length of at least 0.2 cm of the first longitudinal end portion of the overlaying adhesive tape strip still adhered to the second end portion of the intermediate adhesive tape strip.
The novel W-stacked pads of tape strips capable of being dispensed using the novel technique described herein comprises a plurality of superimposed tape strips wherein (i) sequential tape strips are longitudinally reversed so as to align the first end of each tape strip with the second end of an immediately overlaying and an immediately underlying tape strip, (ii) the adhesive layer of each tape strip adheres the second end portion of each tape strip to the first end portion of an adjacent tape strip at a second adhesion level having an adhesive strength sufficient to prevent any appreciable longitudinal movement of the second end portion of an intermediate tape strip relative to the first end portion of an immediately underlying tape strip when an immediately overlying tape strip is dispensed from the pad at a high peel angle, and (iii) the adhesive layer of each tape strip adheres the first end portion of each tape strip to the second end portion of an adjacent tape strip at a first adhesion level, with (A) the first adhesion level having an adhesive strength greater than about 1xc2xd times the adhesive strength of the second adhesion level, and (B) the first adhesion level having an adhesive strength effective for affording a complete release of the overlying tape strip from the intermediate tape strip after the second end portion of the intermediate tape strip is released from the first end portion of the immediately underlying tape strip and before the intermediate tape strip is completely peeled from the second end portion of the immediately underlying tape strip.
Advantageously, the pads and dispenser(s) of the present invention provide the capabilities of constructing pads that when coated appropriately may provide uniform appearance, which in turn facilitates writable surfaces, gloss control, broader range of LAB and adhesive chemistry systems and the like.
As used herein:
xe2x80x9cadhesive strengthxe2x80x9d means the force required to achieve release of an adhesive from another adjacent surface as measured in accordance with ASTM D3811 (xe2x80x9cUnwind Strengthxe2x80x9d);
xe2x80x9cadhesive tape stripxe2x80x9d means a longitudinally elongated strip of a substrate having first and second opposite major surfaces coated with a continuous or discontinuous layer of an adhesive on the second major surface of the substrate;
xe2x80x9ccontinuousxe2x80x9d when used to describe a coating or layer (e.g., LAB coating), means that the coating or layer covers the entire surface area such that the underlying surface (e.g., substrate) is completely covered;
xe2x80x9cdiscontinuousxe2x80x9d when used to describe a coating or layer (e.g., LAB coating), means that the coating or layer is pattern coated (e.g., dot matrix, laterally spaced parallel lines, crosshatching, etc.) and covers less than the entire surface area such that portions of the underlying surface (e.g., substrate) remain exposed;
xe2x80x9cdispensedxe2x80x9d when used to describe manipulation of an adhesive tape strip, means to grasp the second longitudinal end portion of the adhesive tape strip projecting from the pad and pull the adhesive tape strip so as to peel the adhesive tape strip away from the pad until the full length of the adhesive tape strip detaches from the pad and the first longitudinal end of the adhesive tape strip is separated from the second longitudinal end of the adjacent adhesive tape strip;
xe2x80x9cdispensing lengthxe2x80x9d means that portion of the longitudinal length of an overlaying tape strip still adhered to the second longitudinal end portion of an intermediate tape strip at the time the overlaying tape strip contacts a finger on the dispenser and the peel angle is decreased below 45xc2x0 and the xe2x80x9cdispensing lengthxe2x80x9d is primarily dictated by the longitudinal (length) and transverse (height) positioning of the finger relative to the overlying tape strip on the pad retained within the dispenser;
xe2x80x9crelease lengthxe2x80x9d means the longitudinal length of an overlaying tape strip still adhered to a second longitudinal end section of an intermediate tape strip at the time the second longitudinal end section of the intermediate tape strip is separated from an underlying tape strip;
xe2x80x9cdifferential releasexe2x80x9d when used to characterize an adhesive tape strip, means that the longitudinal end portions of the adhesive tape strip adhere to an underlying tape strip at different adhesion levels, such that the force required to separate sequential tape strips is greater at one longitudinal end than at the other longitudinal end;
xe2x80x9ctail offxe2x80x9d when used to describe faulty dispensing of tape strips from a tape strip pad, refers to those situations where an overlaying tape strip separates from an intermediate tape strip without lifting the second longitudinal end of the intermediate tape strip from an underlying tape strip a distance sufficient to permit the second longitudinal end of the intermediate tape strip to engage the dispenser and remain spaced from the underlying tape strip so as to facilitate subsequent dispensing of the intermediate tape strip and includes both the phenomenon known as xe2x80x9cwalk offxe2x80x9d (i.e., the overlaying tape strip separates from an intermediate tape strip without lifting the second longitudinal end of the intermediate tape strip) and the phenomenon known as xe2x80x9cfall backxe2x80x9d (i.e., the second longitudinal end of the intermediate tape strip is separated from the underlying tape strip during dispensing of the overlying tape strip, but does not separate far enough to prevent the intermediate tape strip from returning to the pad and re-engaging the underlying tape strip when the overlaying tape strip separates from the intermediate tape strip);
xe2x80x9cpoint of releasexe2x80x9d means the longitudinal position of the point of departure when the second longitudinal end of the intermediate tape strip releases from the first longitudinal end of the underlying tape strip;
xe2x80x9cpeel anglexe2x80x9d means the angle between an adhesive tape strip being peeled from the pad and an immediately adjacent tape strip on the pad, measured at the point of departure (i.e., the location along the longitudinal length of the adjacent adhesive tape strips where the strips lose contact with one another)
xe2x80x9chigh peel anglexe2x80x9d means a peel angle of greater than about 45xc2x0;
xe2x80x9clow peel anglexe2x80x9d means a peel angle of less than about 45xc2x0, preferably between about 10xc2x0 and 45xc2x0;
xe2x80x9cpoint of departurexe2x80x9d means the position along the longitudinal length of adjacent overlying and intermediate adhesive tape strips where the strips lose contact with one another as the overlying tape strip is peeled from the intermediate tape strip; and
xe2x80x9cW-stacked pad of adhesive tape stripsxe2x80x9d means a pad of superimposed differential release adhesive tape strips with the adhesive layer of each tape strip releasably adhered to an adjacent tape strip and sequential tape strips longitudinally reversed so as to align the first end of each tape strip with the second end of an immediately overlaying and an immediately underlying tape strip, whereby the adhesive layer of each tape strip adheres the second end portion of each tape strip to the first end portion of an adjacent tape strip at a second adhesion level and adheres the first end portion of each tape strip to the second end portion of an adjacent tape strip at a first adhesion level.